No overdrive

[rodb]

Today I disconnected the plug that goes to the trans solenoids, at 60 mph rpm is at 3000. Plugged back in at 65 mph tac reads same rpm 3000, this confirms overdrive is working. Also tapped brake at freeway speed and the converter is unlocking as intended. Still don't understand why this truck revs to 3000 rpm at 65mph. I do have the 3.73 rearend gears, so maybe this is ok. Any thoughts ?

 

[natenkiki2004]

I'd have to check and see what mine is exactly but I know mine is significantly lower than 3,000 RPM and I've got stock tires and 3.73 gears. I'm thinking 2,200-2,500RPM at about 60.

One thing to note, the dash gauges aren't always 100% correct. For ***** and giggles, you might buy a hung-lo-charlie chinese tachometer on eBay that runs off a spark plug wire. See if your dash tach is correct. I know on my 1991 that it can vary day to day. Some days I idle at 1,100RPM while some days it's 800. It's not the engine or IAC, it's the actual tach reading wrong. Happens going down the road too, torque converter will engage at different RPM. Ground going bad or funky connection or something. So, there's that to think about.

 

[natenkiki2004]

I had an opportunity on the highway and actually remembered this thread and decided to check my MPH to RPM. At 65 the RPM is about 2,800. It hits 3,000 at about 70MPH. That's not terribly far off from what you were seeing.

 

[2stroke]

I had an opportunity on the highway and actually remembered this thread and decided to check my MPH to RPM. At 65 the RPM is about 2,800. It hits 3,000 at about 70MPH. That's not terribly far off from what you were seeing.

Then you were stuck in 3rd gear too. You should be just under 2200 at 65 mph.

 

[rodb]

Then you were stuck in 3rd gear too. You should be just under 2200 at 65 mph.

If you read my post #61 it is clear to me that overdrive is indeed working. Not sure if it makes alot of difference but my tires are only 27.5 " tall.

 

[natenkiki2004]

Then you were stuck in 3rd gear too. You should be just under 2200 at 65 mph.

Well, crap.

I'll run through similar diagnostics but I do know that I get a gear change around 45-50MPH that drops RPM significantly. Maybe we're both getting OD/4th but we're missing torque converter lockup?

Or maybe our tachs are just messed up? Being that we both have 1991's, maybe there's issues in the gauges/wiring that cause the reading to be off.

 

[natenkiki2004]

I just came back from a test drive into town, shot some videos and my transmission is working exactly as it should. I feel shifts when they're commanded by the computer. Once the video is edited and uploaded, I'll share it here.

Maybe me and rodb have to chalk it up to the 1991 computer, changes in the A4LD or a tachometer that's out of calibration. I have a cheapie inductive tach that I'll slap on and go for a test drive later for comparison, that'll be another video.

https://www.youtube.com/watch?v=0dowy4Yf1WE

 

[2stroke]

If you read my post #61 it is clear to me that overdrive is indeed working. Not sure if it makes alot of difference but my tires are only 27.5 " tall.

That would put you about 2250 rpm at 65 mph.

 

[rodb]

Great video Nate, was hoping you filmed the speed at 65 to see where your rpm was in overdrive. When in drive mine looks the same as yours.

 

[natenkiki2004]

Great video Nate, was hoping you filmed the speed at 65 to see where your rpm was in overdrive. When in drive mine looks the same as yours.

I'll do that tomorrow. Where I'm heading is a long straight stretch so I can get up to and past 65.

 

[rodb]

Based on your video, looks like you will be around 3,000 rpm @ 65 mph when in overdrive. Looking forward to your upcoming video.

 

[natenkiki2004]

Based on your video, looks like you will be around 3,000 rpm @ 65 mph when in overdrive. Looking forward to your upcoming video.

I didn't end up making one, ran out of time and I didn't like the t-pins sticking out from my computer for an extended period of time. I did spend some time getting accurate numbers in a previous post though:

I had an opportunity on the highway and actually remembered this thread and decided to check my MPH to RPM. At 65 the RPM is about 2,800. It hits 3,000 at about 70MPH. That's not terribly far off from what you were seeing.

 

[rodb]

After watching your video several times, I think you will be seeing at least 3,000 rpm in overdrive when traveling at 65 mph.

 

[natenkiki2004]

After watching your video several times, I think you will be seeing at least 3,000 rpm in overdrive when traveling at 65 mph.

Keep in mind, the video was shot from the left of the center of the steering wheel and the view of the tach is skewed compared to where the driver views it from. It probably looks higher than it is. My previous statement about 3,000RPM at 70MPH is dead on, looking at the tach straight.

 

[rodb]

The saga continues: Today while driving, pulled into parking lot, truck died in gear, put into park, truck starts up right away, shift into drive or reverse truck dies instantly. Pulled the plug in engine compartment that goes to trans shift/overdrive solenoid, restart motor, give lots of throttle and put into gear, now it bogs way down and won't move. Looks like its either locked up torque converter or one of the two shift solenoids. Unreal !!!

 

[2stroke]

Your tach isn't accurate at all. You were accelerating very slowly, you shouldn't have been anywhere near 3000 rpm. Plus your needle jumps around and doesn't respond to the shifts. On top of that TC lockup is not a 1000 rpm drop. The numbers I posted are accurate for true rpm in OD.

 

[natenkiki2004]

Your tach isn't accurate at all. You were accelerating very slowly, you shouldn't have been anywhere near 3000 rpm. Plus your needle jumps around and doesn't respond to the shifts. On top of that TC lockup is not a 1000 rpm drop. The numbers I posted are accurate for true rpm in OD.

I never claimed my tach was accurate I just know the transmission is shifting properly. I did mention some deviances in my tach. Whether it's just due to a bad ground or gauge cluster that's going funky, I don't know. My speedometer jumps around, I don't think I've seen the tach do that. It does respond to shifts though, you can see drops if you know when to look.

I haven't gotten around to comparing my tach to an inductive one but it just goes to show that just because the numbers are off doesn't mean that the transmission is faulty. I did say earlier that my tach varies for both idle and TCC lockup. I've also seen the tach totally drop out while driving. It never affects the engine so I know it's the wiring from the ICM to the gauge, not something the computer is seeing so it's not really a concern.

I'm glad I made the video because you may not always feel a shift, I find the higher gears are softer for some reason. But combine the feel, tach and voltage and you know without a doubt that the transmission is indeed shifting when the computer commands it.

 

[rodb]

Today put the truck in air on jacks, started up and put into drive and reverse, it does not die now, what does this indicate? Really like this truck and don't want to give up.

 

[2stroke]

I simply didn't want to lead rodb to think 3000 rpm was normal for OD.
[MENTION=210050]rodb[/MENTION]

When you put it in reverse, but stepped on the brake the engine continued to run?

 

[natenkiki2004]

I simply didn't want to lead rodb to think 3000 rpm was normal for OD.

Right, and I don't want to spread misinformation either. But it's something to consider, just because the tach is at 3000, doesn't mean the trans is bad. His being a 1991 like mine, there may be a (yet another) teething issue that Ford had with the cluster or wiring harness. Or it's just age.

Unfortunately rodb is a bit beyond that. Definitely putting the trans under load would help. Just be safe with the jacks and a vehicle in gear.